We have investigated the far-infrared (FIR) responses of an array of quantum dots in modulation doped GaAs heterostructures in an external magnetic field. In accordance with the extended Kohn theorem FIR-radiation can only excite the center-of-mass modes of harmonically confined electrons in a dot. In a perpendicular magnetic field the single absorption peak corresponding to the Kohn mode splits in two peaks separated by the cyclotron frequency. We observe novel modes at frequencies below the higher frequency Kohn mode. Comparison with Hartree-RPA calculations show that these modes arise from the flattened confining potential in our field-effect quantum dots. They reflect t pronounced relative motion of the charge density with respect to its center-of-mass.
|Number of pages||4|
|Journal||Physica Scripta T|
|Publication status||Published - 2002|
|Event||Proceedings of the 19th Nordic Semiconductor Meeting - Lyngby, Denmark|
Duration: 20 May 2001 → 23 May 2001